PROJECT SUMMARY There is an urgent need to gain a greater understanding of basic biological mechanisms in autism spectrum disorders (ASDs) as a path to discover new therapeutic targets. In this proposal, we aim to leverage cutting- edge genomic technologies together with the unique advantages of zebrafish to investigate the effect of loss of function of two top ASD risk genes, CHD8 and SCN2A, on translation regulation in the developing brain. Our central goal is to elucidate the mechanisms by which loss of function of these genes affects translation in both neurons and glia, predisposing to cell type-specific deficits. Our central hypothesis is that ASD gene disruption will lead to alterations in the global translatome in the developing vertebrate brain, predisposing to cell type-specific abnormalities. This hypothesis is based on our compelling preliminary data demonstrating that translation is a significantly dysregulated pathway in whole-brain RNA-seq of zebrafish mutants of three top ASD risk genes, all of which display robust behavioral, brain structural and activity phenotypes. To test this hypothesis, we will perform Translating Ribosome Affinity Purification sequencing (TRAP-seq) using a novel zebrafish Ribo-Tag transgenic line to evaluate actively translated mRNAs in neurons and glia derived from whole brains of zebrafish mutants of chd8 and scn1lab (Aim 1), and single cell RNA-seq (scRNA-seq) to characterize cell type-specific differences in mutants (Aim 2). We expect that our highly innovative and exploratory approach will provide new insights into how two top ASD risk genes affect translation regulation and cell type composition in the developing vertebrate brain. The expected outcome of this research is to advance our understanding of translation as a central regulatory mechanisms underlying ASDs. This research will advance the field by illuminating a novel targetable pathway downstream of ASD genes with potential therapeutic implications.